This is an easy project that I use at the start of my 7-week beginner sewing class. It gives students a real sense of accomplishment right away!
Cut two rectangles 4"x5" and one piece of elastic 4 5/8" long. Make a sandwich: fabric is right sides together with the elastic in between. Machine sew with 1/2" seam allowances, leaving a 2 1/2" opening in one side. Clip corners diagonally across without cutting the stitches (this reduces bulk). Turn the cushion right side out. Stuff firmly. Slip stitch the opening shut. Ta Da! My beginning students love this because the very first night they leave with a finished project and in the process they learned about grain lines (my cardboard patterns have this marked on it), cutting out and measuring, sewing on the machine and keeping seam allowances even, stuffing and hand sewing. They can now make a simple pillow!